Some multiple borehole systems, particularly those that include deviated or horizontal portions, typically require some form of monitoring to avoid intersecting the boreholes. For example, Steam Assisted Gravity Drainage (SAGD) systems include an injection borehole that provides a heat source (e.g., steam) for heating bitumen and/or heavy oil, and a recovery borehole to collect and produce the bitumen and/or heavy oil. The boreholes are typically maintained generally parallel at a selected distance from one another. Thus, monitoring or detection should be employed to allow for accurate directional drilling of the boreholes.